The long term storage of silver halide color photographs in the same condition as that obtained immediately after development is very important when considering the possible use of photographs as records. A great deal of research effort has therefore been directed at this point. The stability of the dye images is an important factor in respect of the long term storage of color photographs.
The dye images of silver halide color photographic materials are known to fade markedly, depending on the storage conditions, when they are stored for a long period of time in light, and also when they are exposed to light for short periods of time and stored for long periods of time in the dark. In general, the color fading in the former case is called light fading and that in the latter cases is called dark fading, and when color photographic materials are stored semipermanently as records it is desirable that the extents of light fading and dark fading should be reduced to a minimum and that the overall color balance of the faded tricolor yellow, magenta and cyan dye images should be maintained in the initial state. However, the extents of light and dark fading differ for each of the yellow, magenta and cyan dye images, and after long term storage the aforementioned overall faded color balance is inevitably destroyed and the picture quality of the dye image inevitably deteriorates.
The extents of light fading and dark fading differ according to the couplers which are used and other factors but, in many cases, dark fading arises most readily in the case of the cyan dye image, followed in order by the yellow dye image and the magenta dye image, and the extent of the dark fading of the cyan dye image is greater than that of the other dye images. Furthermore, in the case of light fading, the magenta dye image tends to fade most readily when a visible light source is used, followed in order by the cyan dye image and the yellow dye image.
Thus, in order to maintain a good faded color balance between the yellow, magenta and cyan dye images over a long period of time it is necessary to reduce to a minimum the light and dark fading of the cyan dye image, and various attempts have been made in the past with a view to improving light and dark fading properties for this purpose. These past attempts can be broadly classified into two categories, namely those in which novel couplers which can form dye images which are less liable to fading have been developed and those in which novel additives which prevent fading from occurring have been developed.
The former of these methods have been widely researched (U.S. Pat. No. 2,801,171, JP-B-49-11572, U.S. Pat. No. 2,895,826, JP-A-55-163537 and JP-A-56-104333, U.S. Pat. Nos. 3,767,4125 and 4,03,716 and JP-B-48-30494, etc.) (the term "JP-A" as used herein signifies an unexamined published Japanese patent application, and the term "JP-B" as used herein signifies an examined published Japanese patent application), but not so many reports have been published in connection with the latter methods mentioned above, and as yet no effective method which can be used without some adverse effect has been discovered.
A second important point in respect of the long term storage of color photographs involves the prevention of coloration of the white background which is to say the prevention of the occurrence of staining due to light and heat. The occurrence of staining can be broadly classified as that which is caused by the degradation of organic materials which are present in the photosensitive material from the start and that which is due to development bath components, especially primary aromatic amine compounds which are the developing agents and compounds derived therefrom, which are left behind in the photosensitive material after development processing. This staining not only causes coloration of the white base but also has a further disadvantage in that it reduces the image saturation of a color photograph.
Silver halide color photographs reproduce a colored image with the three colors yellow, magenta and cyan but, of these, the hue of the magenta is of particular importance from the viewpoint of color reproduction. Progress has been made recently with the improvement of the magenta couplers which form the magenta dyes, and magenta couplers, such as the pyrazoloazole based couplers (U.S. Pat. No. 4,540,654, JP-A-61-65245, etc.), which have a sharp spectral absorption without the subsidiary absorption in the vicinity of 430 nm, which is a major disadvantage of the existing 5-pyrazolone based couplers (JP-A-49-74027, JP-A-49-111631, etc.), have been discovered and put to practical use. The color reproduction in a silver halide color photograph is greatly improved by using these couplers, but the occurrence of staining during storage has become an even greater problem that it was in the past.
Effective methods for preventing the occurrence of this staining have been proposed in U.S. Pat. Nos. 4,463,085 and 4,483,918, in JP-A-59-218445 and JP-A-59-229557 and in U.S. Pat. Nos. 4,358,525, 4,465,762, 4,522,917 and 4,661,440, etc., but as yet these have proved to be unsatisfactory as a means of preventing the occurrence of staining to a sufficiently high level.